The funerals will take place today of a 19-year-old man and a garda killed in a crash at the weekend.
The Garda Síochána Ombudsman Commission and the Garda Síochána are conducting separate inquiries into the circumstances which led to the deaths of Garda Terry Dever (48), a father of three from Achill island, Co Mayo, and Stephen Conway, a single man from Inver, Co Mayo.
The commission investigates all matters involving loss of life if a member of the force is involved.
The head-on collision occurred at about 5.50am on Sunday, when Garda Dever and two of his colleagues were travelling from Achill island in two private cars to begin a 6am shift at Belmullet Garda station.
In a statement, the commission said that the three gardaí in two private cars "encountered a car coming in the opposite direction".
"The first car, carrying one garda, narrowly avoided a collision with this vehicle. The second car, carrying two gardaí, was involved in a collision with the oncoming car. The driver of the oncoming car was fatally injured when his car collided with the car travelling in the opposite direction which was occupied by the two off-duty gardaí," the commission said.
"He was removed to Mayo General Hospital in Castlebar. He was pronounced dead not long after the incident," the commission said.
Garda Dever was very involved in his community and in sport and music in Saulia, Achill, where he lived with his wife Margaret, and three children, Liam, Alice and Turlough.
Mr Conway, who was the youngest son of Val and Kathleen Conway, had recently finished school and was working in a restaurant in Belmullet. He was a nephew of Terence Conway, spokesman for Shell to Sea Mayo, but had no involvement in a protest at the Glengad site on Saturday evening.